This invention relates to dental impression trays, and more particularly to a method and apparatus for forming negative impressions of dental areas in a patient's mouth.
In connection with performing restoration of defective dental areas, it is frequently necessary to form negative impressions of the dental area which is to be restored. In order to form such negative impressions, it is generally well known in the dental art to utilize a dental impression tray. Such trays are typically arcuately shaped in plan, and have a substantially U-shaped cross-sectional configuration so as to provide a trough for receiving dental impression material.
Typically, the trough of the dental impression tray is first filled with the dental impression material, and the filled impression tray is then seated on the dental area to be restored. Pressure is applied onto the dental impression tray so as to press the teeth into the dental impression material to form a negative impression within the material. The tray is generally held in the mouth until the impression material hardens and is then removed from the mouth. Subsequent steps are then carried out in accordance with conventional practices.
One problem with utilizing such dental impression trays is that much of the dental impression material will be forced out between the impression tray and the dental area, and form a flash about the dental area to be restored. Additionally, by pressing down directly onto the tray, a direct force is applied onto the dental area and frequently, where the dental area is weak, defective, or loose, breakage of the dental area is possible. Also, it is difficult to actually see the dental area when covered with the tray, and to determine whether a suitable negative impression has been made.
In order to alleviate some of these problems, apertures are formed in the dental impression tray, especially in the bottom wall of the tray. By means of such apertures, the flash is reduced since the excess dental impression material flows through the apertures and out of the tray itself. Although the use of the apertures alleviates some of the problems concerning the flash, it introduces new problems since inaccurate negative impressions might be achieved. When utilizing an apertured dental impression tray, as the force is being applied onto the tray so as to seat the tray on the dental area, a resisting force is being provided by the teeth into the impression material. This resisting force pushes the impression material through the apertures of the tray and away from the teeth. As a result, the dental impression material does not flow completely around the dental area and, as a result, portions of the dental area may not be completely surrounded by the dental impression material. For example, the space between adjacent teeth may not be completely filled with the impression material since both adjacent teeth will push the impression material through the tray apertures and, accordingly, suitable negative impressions may not be formed.